Two temperature refrigerator



Dec. 26, 1967 F. STEVENS TWO TEMPERATURE REFRIGERATOR 2 Sheets-Sheet 1Filed Oct. 14, 1966 5 All]! SOURCE INVENTOR. Fran/r L. Stevens BY KDe.2s, 1967 F. L. STEVENS 3,359,751

TWO TEMPERATURE REFRIGERATOR United States Patent 3,359,751 TWOTEMPERATURE REFRIGERATOR Frank L. Stevens, Galesherg, Ill., assignor toAdmiral Corporation, Chicago, 111., a corporation of Delaware Filed Oct.14, 1966, Ser. No. 586,730 8 Claims. (Cl. 62-186) This invention relatesin general to refrigerators having two separate refrigeratedcompartments in side-by-side relationship, and in particular to suchrefrigerators employing a single evaporator coil for cooling bothcompartments. More particularly, this invention relates to sideby-sidecombination refrigerator-freezers employing a single evaporator coil andcooperating temperature responsive means for individually controllingthe temperature of each compartment in a manner which precludesexcessive compressor running time and abnormally frequent compressorcycling.

Side-by-side combination refrigerator-freezers employing a commonvertical dividing wall and separate compartment access doors, have beenfamiliar to the domestic refrigeration industry for many years. However,only recently have such combinations met with consumer acceptance, andnow they account for a substantial percentage of the total number ofunits being manufactured. Major factors leading to such consumeracceptance are the convenience of a separate below freezing compartmentadjacent the above freezing compartment, thin wall insulation whichallows a greater refrigerated volume in a given space, substantial costreductions without'sacrificing performance, and decorator acceptance oftwo doors in sideby-side relationship, rather than the doors beingstacked one above the other.

Typical early construction of side-by-side combinationrefrigerator-freezers comprised separate above freezing and belowfreezing compartments wherein each compartment had an independentrefrigeration system basically comprising a motor-driven compressor, acondenser, restricting means, and an evaporator. Within a short time,due to the expense of two independent refrigeration systems, thecomponents of the second system, except the evaporator, were eliminated.Thus, a single motor-driven compressor and individual evaporators,either with or without circulating fans, were utilized to cool the abovefreezing and below freezing compartments.

Refrigerators using a single compressor and individual evaporatorstypically had a single thermostat located in one of the compartments forcontrolling compressor operation. The thermostat was generallymaintained in the above freezing compartment sincein the average homethe access door thereto is opened more frequently than the door to thebelow freezing compartment. Consequently, when the above freezingcompartment was opened more than normal, or was left open for anunusually long duration, the compressor operated continuously for longperiods to satisfy the thermostat and the below freezing compartment wasmaintained at a much lower temperature than was desirable. While thiswas not detrimental from a standpoint of food storage, the unnecessarymaintenance of a compartment at such low temperatures resulted in costlyrefrigerator operation.

This invention obviates many of the difficulties, deficiencies, andinadequacies of prior art side-by-side combination refrigerator-freezersby utilizing a single evaporator coil located in the below freezingcompartment. A dual fan system provides air circulation in the belowfreezer compartment through a major portion of the evaporator, andprovides circulation from the above freezing compartment through only anedge portion of the same evaporator. While air from both the abovefreezing and below freezing compartments circulate through the sameevaporator, a bafile is utilized to substantially isolate each air flow,thereby preventing air in the below freezing compartment fromcommingling with air in the above freezing compartment. In addition, aseparate thermostat and fan is provided for each compartment to insureadequate circulation and rapid temperature recovery, and for minimumcompressor cycling.

Accordingly, it is the primary object of this invention to provide aside-by-side combination refrigerator-freezer having a singlerefrigeration system employing a single evaporator coil.

Another object of this invention is to provide a side-byside combinationrefrigerator-freezer wherein the temperature of each compartment may beindividually con trolled by means which preclude lengthy continuouscompressor operation or undue compressor cycling.

An additional object of this invention is to provide a side-by-sidecombination refrigerator-freezer having a thermostatic temperaturesensitive element in the below freezing compartment which is located soas to minimize continuous compressor ope-ration and undue compressorcycling by being responsive to the temperatures of the below freezingand above freezing compartments.

A further object of this invention is to provide a frost freeside-by-side combination refrigerator-freezer having counter-flow airmovements through a single evaporator coil for more advantageous frostaccumulation and subsequent defrosting of the above freezing section ofsaid evaporator coil, and for more natural circulation through the belowfreezing section thereof.

It is also an object of this invention to provide a single evaporatorcoil for a two temperature refrigerator wherein said evaporator coil isvoid of heat exchange fins in the section thereof having the greatestexposure to moisture, thereby precluding the possibility of a rapidaccumulation of frost from causing blockage of air movementtherethrough.

Other objects of this invention will become apparent upon an examinationof the following description taken in conjunction with the accompanyingdrawings wherein:

FIG. 1 is a three dimensional front view of a side-byside combinationrefrigerator-freezer in which the invention is incorporated, having itsaccess doors in an open position.

FIG. 2 is a skeleton view of a side-by-side combinationrefrigerator-freezer showing the location of the single evaporator, thetwo fans, and the air flow pattern for each compartment.

FIG. 3 is an enlarged elevation view taken along line 3-3 of FIG. 2,showing in detail the single evaporator, the location of the fans, andthe location of the thermostat sensing bulb in the below freezingcompartment.

FIG. 4 is a schematic drawing of an electrical system for a side-by-sidecombination refrigerator-freezer incorporating the invention.

Turning to consideration of the drawings and in particular to FIG. 1,there is shown an automatic defrosting, side-by-side combinationrefrigerator-freezer which includes a cabinet 10 comprising side walls12 and 14, a rear wall 15 extending between the side walls, and a commonvertical dividing wall 16 dividing the cabinet into a below freezingcompartment 18 and an above freezing compartment 20, each of which hasits own access door 22 and 24, respectively. The below freezingcompartment includes a motor driven fan 26 for circulating air thereinand a thermostat 27 having a control knob 28 for controlling thecompartment interior temperature. The above freezing compartment isequipped with a separate thermostat 30 having a control knob 32 and asensing element 34 for sensing the interior temperature thereof.

Referring now to FIGS. 2 and 3, a rectangular evaporator, generallyreferred to by reference numeral 40, is mounted on the upper half ofrear wall 15, parallel thereto. The evaporator is fabricated in a mannerwellknown to those familiar with the domestic refrigeration art andbasically is of the fin and tube construction. Evaporator tubing 42 isformed into a coil having a serpentinelike configuration, the straightportions of which are bonded to a series of vertical fins 44 for goodheat transfer thereto and increased heat transfer surface area. Avertical baffle 46 located adjacent one end of the straight tubingportion (best seen in FIG. 3) divides the evaporator into two evaporatorpassages, a first passage 48, and a second passage 50.

First evaporator passage 48 comprises the straight portions of tubing 42and vertical fins 44, and functions to cool below freezing compartment18. Evaporator passage 50 primarily comprises U shaped end loops 51 ofthe serpentine coil which are void of heat transferring fins. The endloops function to absorb heat from the air circulating through passage50 from the above freezing compartment, in a manner to be explainedbelow.

The evaporator also includes a defrost heater 45 which is merely aresistance wire in contact with the fins and tubing for periodicallymelting frost accumulations.

The evaporator is the cooling element of the refrigeration system whichalso includes a motor-driven compressor 52, a condenser 55 and acapillary tube 57, or other suitable refrigerant restricting means.Operation of the refrigeration system comprising compressing, cooling,expanding, and evaporating the refrigerant gas contained in the system,is well-known by those in the art and need not be described in detail.

Air in the below freezing compartment circulates in a substantiallyrectangular pattern as indicated by the broad cross-hatched arrows ofFIG. 2. The pattern is established by below freezing compartment fan 26which forces air into the top of first evaporator passage 48, and intoheat transfer relationship with tubing 42 and fins 44. The cooled air isdischarged through the bottom of the evaporator passage, and into thebelow freezing compartment. The pattern of air flow in this compartmentis assisted by natural convection, that is, the cold air seeks a lowerlevel through the evaporator, and the warm air tends to rise.

An evaporator cover 54 overlays the front of evaporator 40 and includesa protective grill 56 in front of fan 26 to preclude accidentalinterference therewith. The below freezing compartment thermostat 27includes a temperature sensing bulb 58 secured in intimate contact withthe back surface of evaporator cover 54, opposite and slightly aboveevaporator passage 48, and directly beneath fan 26. Thermostat 27controls operation of freezer compartment fan 26 and compressor 52, i.e.the refrigeration system.

While fan 26 and compressor 52 are idle, sensing bulb 58 primarilysenses the interior temperature of the below freezing compartment byconduction through the evaporator cover, although, as the evaporatorabsorbs heat from the above freezing compartment in a manner to beexplained below, sensing bulb 58 may also be influenced by conductionthrough the evaporator tubing. During operation of fan 26, therelatively warm air at the top of the below freezing compartment passesdirectly over bulb 58 before being cooled, thus the thermostat is onlyactuated when the compartment is thoroughly cooled. This provides longercontinuous compressor running time and less compressor cycling, withimproved operating efiiciency.

The above freezing compartment is cooled by passing air from it throughsecond evaporator passage 50 containing end loops 51, which will berecalled are void of fins. To accomplish this, a diagonal duct 60 isprovided within the confines of vertical dividing wall 16. Duct so hasan inlet 62 at the bottom of the above freezing compartment, and anoutlet 64 at the bottom of the second evaporator passage in the belowfreezing compartment. The duct provides a conduit for moving air fromthe above freezing compartment into the second evaporator passage. Afterpassing through the second evaporator passage and being cooled by theevaporator end loops, the air is returned to the above freezingcompartment via a second duct 66 having its inlet 68 at the top of thesecond evaporator passage and having its outlet '70 connected to anopening 74 provided through vertical dividing wall 16.

A fan 72 is mounted in opening 74 for establishing the air pattern inthe above freezing compartment. This pattern comprises moving air fromthe above freezing compartment upwardly through duct 60, evaporatorpassage 50 and duct 66, then returning it to the original compartmentthrough opening 74. The cold air slowly migrates to the bottom of theabove freezing compartment to be drawn upwardly again through duct 60.This air fiow pattern can be clearly seen in FIG. 2 and is representedby the narrow solid arrows shown therein.

The air in the above freezing compartment typically has a high relativehumidity due to the nature of the foods usually stored therein. As theair from this compartment circulates through second evaporator passage50, frost will accumulate on the evaporator end loops which typicallyare maintained at a temperature of about -10 F. During initial coolingof the above freezing compartment, when the relative humidity is veryhigh, the frost build-up can be so severe as to cause a substantialrestriction of the passage if the evaporator were contructed in aconventional manner. This is obviated by eliminating the heat transferfins from the evaporator end loops which prevents a frost accumulationon closely adjacent surfaces. While some loss may be detected in thequantity of heat transferred between the evaporator and the air from thefresh food compartment, this can be compensated for in various ways suchas by providing more pronounced end loops or a greater air flow throughthe passage.

Moist air from the above freezing compartment enters the bottom of thesecond evaporator passage and immediately condenses and freezes on thelower evaporator end loops. Consequently, the greatest quantity of frostwill accumulate in this area. Frost accumulation on the lower evaporatorend loops, rather than on the loops near the top, is advantageous duringthe defrost phase since the frost loosened by the defrost heaters candrop unobstructed to the drip trough 80, where it may be melted bysuitable electrical resistance heaters, not shown.

Operation of fan 72 is controlled by thermostat 30 (FIG. 1) located inabove freezing compartment 20. Sensing bulb 34 for the thermostat issituated in the above freezing compartment, directly in the air streamflowing through opening 74 from the second evaporator passage. The solefunction of thermostat 30 is to control operation of fan 72, and itsoperation is completely independent of compressor 52 and fan 26.

Thermostat 27 for the below freezing compartment, having its temperaturesensing bulb 58 secured to the rear surface of evaporator cover 54,which as explained above, controls simultaneous operation of fan 26 andcompressor 52, is also influenced by operation of above freezingcompartment fan 72. This influence is exerted by relatively Warm airfrom the above freezing compartment moving through evaporator passage50, warming the end loops which vaporizes the refrigerant containedtherein. The vaporized refrigerant expands and flows through theevaporator tubing, especially through the passes at the top, radiatingheat to sensing bulb 58 which actuates the thermostat and turns on thecompressor and fan 26.

Unnecessary compressor cycling attributed to cooling the above freezingcompartment is prevented in a novel manner. The sensing bulb forthermostat 27 is positioned at the top of the evaporator, which is thelast portion to be warmed. Thus, the temperature of the entireevaporator must be increased before heat is radiated to the sensing bulbfor actuating thermostat 27. Under normal operating conditions, fan 72may cycle on and off several times before the entire evaporator isheated sufiiciently to actuate thermostat 27 since the specific heat ofthe evaporator section in passage 48 is large'compared to theheat'absonbed in cooling the above freezing compartment.

Turning now to FIG. 4, a schematic diagram of the compressor and fansfor the two temperature refrigerator described, is shown. An A.C. sourcesupplies power to motor-driven compressor 52 and the parallellyconnected fan motor 26, which operate simultaneously. A snap actionelectric switch, having contacts 29, serially couples the source to thecompressor and fan for controlling energization thereof. The switch isactuated by thermostat 27 mounted in the above freezing compartmentwhich, as will be recalled, has its sensing element 58 secured totheback side of evaporator cover 54. The AC. source is also connected tofan motor 72 which is controlled by a second snap action switch 31. Thisswitch is actuated by thermostat 30, which has its sensing element 34 inthe above freezing compartment.

A defrost timer 84 is provided to insure adequate defrost of evaporator40 as specified time intervals during the day. This timer energizesdefrost heater 45 which rapidly heats the evaporator and melts any frostaccumulation. Water from the evaporator drips into a drain trough 80 andis piped to a convenient receptacle for disposal, such as a moistureevaporating pan, not shown.

In operation, the side-by-side combination refrigeratorfreezer isdesigned to operate as follows. The below freezing compartmentthermostat closes electrical contacts 29, energizing fan 26 and thecompressor, at approximately +8 F. They operate continuously until thetemperature of the \below freezing compartment reaches approximately +2F. During this time, above freezing compartment fan 72 may or may not beoperating, depending upon the temper-anire of that compartment. This fanonly operates responsive to thermostat 30 Which is preferably adjustedto close electrical contacts 31 at a temperature of +36 F. and open themat +31 F., and of course is capable of operating while the compressor isoff. Fan 72 moves air through evaporator passage 50 and into the abovefreezing compartment, thereby reducing its temperature until bulb 34senses that the compartment is satisfied. Thermostat 30 then openscontacts 31, tie-energizing the fan. Eventually, heat conducted toevaporator end loops 42 will be sensed by thermostat sensing bulb 58thereby initiating operation of fan 26 and the compressor.

It should be noted that during the entire operation of either or bothfans, air passing from the above freezing compartment through the secondevaporator passage is entirely segregated from air passing through thefirst evaporator passage, by bafile 46. This complete segregationeliminates the possibility of an extremely cold quantity of air beingconducted into the above freezing compartment, such as exists in manyprior art two-temperature refrigerators. In addition, a localized hightemperature area in the below freezing compartment is prevented byeliminating the entrance of relatively warm air from the above freezingcompartment.

What has been described is a side-by-side combinationrefrigerator-freezer having a single evaporator with segregated airpassages and independent, thermostatically operated fans for providingcirculation through each compartment. Operation of the refrigerationsystem is controlled by a thermostat having a sensing bulb in onecompartment, which is sensitive to the temperature of both compartments.

It is obvious that upon study by those skilled in the art, the disclosedinvention may he altered or modified both in physical appearance andconstruction without departing from its inventive concept. Therefore,the scope of protection to be given this invention should not be limitedby the embodiment described above, but should be determined by theessential descriptions thereof which appear in the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A refrigerator comprising: an insulated cabinet; an insulatedvertical wall dividing said cabinet into a below freezing compartmentand an above freezing compartment, each of said compartments having anaccess opening thereto and movable doors for opening and closing saidaccess openings; a refrigeration system, including an evaporatorvertically mounted on a rear wall of said below freezing compartment;said evaporator including a serpentine like refrigerant conduit having Ushaped end loops, and a vertical evaporator partition positionedperpendicular to said rear wall dividing said evaporator into a firstevaporator passage comprising a major portion of said refrigerantconduit and a second evaporator passage comprising said end loops; meansforming an air passage in said vertical wall having an inletcommunicating with said above freezing compartment and an outletadjacent said. evaporator in said below freezing compartment; and fanmeans for only circulating air in said below freezing compartmentthrough said first evapor'ator passage and only circulating air fromsaid above freezing compartment through said air passage, through saidsecond evaporator passage, and back to said above freezing compartment.

2. The combination as set forth in claim 1 including additionally: aduct extending from one end of said second evaporator passage to anopening through and defined by said vertical dividing wall; said airpassage formed in said vertical dividing wall having its inlet adjacentthe bottom of said above freezing compartment and its outlet adjacentthe remaining end of said second evaporator passage; and wherein saidfan means comprise a first fan mounted in said below freezingcompartment for moving air therein, and a second fan mounted in saidopening for moving air from said above freezing compartment through saidpassage in the vertical well, through said second evaporator passage,and through said duct, thereby returning it to said above freezingcompartment, and means controlling operation of said fans responsive tothe respective temperatures of said compartments.

3. The combination as set forth in claim 2 wherein the refrigerantconduit in said first evaporator passage includes a plurality of spacedapart fins for rapid heat transfer from the air circulatingtherethrough, said fins being subject to only minor frost accumulationthereon due to a normally low moisture content in said below freezingcompartment; and wherein said end loops are void of fins therebyprecluding the occurrence of excessive frost resulting from afortuitously abnormal moisture condition in said second compartmentcausing a rapid frost accumulation thereon and consequent blockage ofsaid second evaporator passage; and heater means in heat transferrelationship with said evaporator for periodic defrosting thereof.

4. The combination as set forth in claim 3 wherein the air from saidabove freezing compartment circulates upwardly through said secondevaporator passage thereby concentrating a fortuitous ice formation atthe lower end thereof for simplified defrosting; and wherein the air insaid below freezing compartment is circulated downwardly through saidsaid first evaporator passage thereby taking advantage of natural airconvection.

5. The combination as set forth in claim 4 wherein said first fan andsaid refrigeration system operate simultaneously responsive to thecon-joint temperatures of said below freezing compartment and of saidevaporator, and wherein said second fan operates responsive to theinterior temperature of said above freezing compartment.

6. The combination as set forth in claim 5 including additionally: anevaporator cover substantially parallel to said rear wall for enclosingthe front of said refrigerant conduit and having one surface thereofexposed to the interior of said below freezing compartment; and whereinsaid means controlling operation of said fans comprise two thermostats;a first of said thermostats controlling operation of said first fan andhaving a temperature sensing bulb secured to said evaporator coveradjacent the major portion of said refrigerant conduit primarily sensingthe temperature of said below freezing compartment by conduction throughsaid evaporator cover, said bulb also sensing a temperature change ofsaid refrigerant conduit caused by heat exchange from air circulatingthrough said second passage; and a second of said thermostats having aseparate temperature sensing bulb located in said above freezingcompartment controlling operation of said second fan, whereby thetemperature of said compartments may be maintained at separate andsubstantially independently regulated levels.

7. The combination as set forth in claim 6 wherein the temperaturesensing bulb of said first thermostat is located in the air stream ofsaid first evaporator passage, adja cent its upper end, for maximumexposure to warm air from said below freezing compartment duringoperation of said first fan and said compressor, whereby said sensingbulb accurately portrays the temperature condition existing within saidbelow freezing compartment and said thermostat allows said compressor tooperate continuously until the below freezing compartment is thoroughlycooled, eliminating unnecessary frequent cycling thereof.

8. The combination as set forth in claim 7 wherein the specific heat ofthe major portion of said refrigerant conduit is relatively large andthe quantity of heat transferred to the air circulated past said endloops by said second fan is relatively small, the temperature of saidevaporator thereby slowly increasing, further eliminating frequentcompressor cycling.

References Cited UNITED STATES PATENTS 2,812,642 11/1957 Jacobs 62-1862,815,649 12/1957 Angelus 62-419 3,027,732 4/1962 Mann 62-419 3,122,8993/ 1964 Constantini 62-419 3,232,071 2/1966 Wallenbrock 62-419 WILLIAMJ. WYE, Primary Examiner.

1. A REFRIGERATOR COMPRISING: AN INSULATED CABINET; AN INSULATEDVERTICAL WALL DIVIDING SAID CABINET INTO A BELOW FREEZING COMPARTMENTAND AN ABOVE FREEZING COMPARTMENT, EACH OF SAID COMPARTMENTS HAVING ANACCESS OPENING THERETO AND MOVABLE DOORS FOR OPENING AND CLOSING SAIDACCESS OPENINGS; A REFRIGERATION SYSTEM, INCLUDING AN EVAPORATORVERTICALLY MOUNTED ON A REAR WALL OF SAID BELOW FREEZING COMPARTMENT;SAID EVAPORATOR INCLUDING A SERPENTINE LIKE REFRIGERANT CONDUIT HAVING"U" SHAPED END LOOPS, AND A VERTICAL EVAPORATOR PARTITION POSITIONEDPERPENDICULAR TO SAID REAR WALL DIVIDING SAID EVAPORATOR INTO A FIRSTEVAPORATOR PASSAGE COMPRISING A MAJOR PORTION OF SAID REFRIGERANTCONDUIT AND A SECOND EVAPORATOR PASSAGE COMPRISING SAID END LOOPS; MEANSFORMING AN AIR PASSAGE IN SAID VERTICAL WALL HAVING AN INLETCOMMUNICATING WITH SAID ABOVE FREEZING COMPARTMENT AND AN OUTLETADJACENT SAID EVAPORATOR IN SAID BELOW FREEZING COMPARTMENT; AND FANMEANS FOR ONLY CIRCULATING AIR IN SAID BELOW FREEZING COMPARTMENTTHROUGH SAID FIRST EVAPORATOR PASSAGE AND ONLY CIRCULATING AIR FROM SAIDABOVE FREEZING COMPARTMENT THROUGH SAID AIR PASSAGE, THROUGH SAID SECONDEVAPORATOR PASSAGE, AND BACK TO SAID ABOVE FREEZING COMPARTMENT.
 2. THECOMBINATION AS SET FORTH IN CLAIM 1 INCLUDING ADDITIONALLY: A DUCTEXTENDING FROM ONE END OF SAID SECOND EVAPORATOR PASSAGE TO AN OPENINGTHROUGH AND DEFINED BY SAID VERTICAL DIVIDING WALL; SAID AIR PASSAGEFORMED IN SAID VERTICAL DIVIDING WALL HAVING ITS INLET ADJACENT THEBOTTOM OF SAID ABOVE FREEZING COMPARTMENT AND ITS OUTLET ADJACENT THEREMAINING END OF SAID SECOND EVAPORATOR PASSAGE; AND WHEREIN SAID FANMEANS COMPRISE A FIRST FAN MOUNTED IN SAID BELOW FREEZING COMPARTMENTFOR MOVING AIR THEREIN, AND A SECOND FAN MOUNTED IN SAID OPENING FORMOVING AIR FROM SAID ABOVE FREEZING COMPARTMENT THROUGH SAID PASSAGE INTHE VERTICAL WALL, THROUGH SAID SECOND EVAPORATOR PASSAGE, AND THROUGHSAID DUCT, THEREBY RETURNING IT TO SAID ABOVE FREEZING COMPARTMENT, ANDMEANS CONTROLLING OPERATION OF SAID FANS RESPONSIVE TO THE RESPECTIVETEMPERATURES OF SAID COMPARTMENTS.